Pgpool-II实现高可用+读写分离+负载均衡（四）---- failover.sh分析

#!/bin/bash# This script is run by failover_command.set-o xtrace
# Special values:# 1)  %d = failed node id# 2)  %h = failed node hostname# 3)  %p = failed node port number# 4)  %D = failed node database cluster path# 5)  %m = new main node id# 6)  %H = new main node hostname# 7)  %M = old main node id# 8)  %P = old primary node hostname# 9)  %r = new main port number# 10) %R = new main database cluster path# 11) %N = old primary node hostname# 12) %S = old primary node port number# 13) %% = '%' characterFAILED_NODE_ID="$1"FAILED_NODE_HOST="$2"FAILED_NODE_PORT="$3"FAILED_NODE_PGDATA="$4"NEW_MAIN_NODE_ID="$5"NEW_MAIN_NODE_HOST="$6"OLD_MAIN_NODE_ID="$7"OLD_PRIMARY_NODE_ID="$8"NEW_MAIN_NODE_PORT="$9"NEW_MAIN_NODE_PGDATA="${10}"OLD_PRIMARY_NODE_HOST="${11}"OLD_PRIMARY_NODE_PORT="${12}"# PostgreSQL目录PGHOME=/usr/local/pgsql16
# 复制槽名称REPL_SLOT_NAME=${FAILED_NODE_HOST//[-.]/_}# 启动PostgreSQL服务的用户名POSTGRESQL_STARTUP_USER=postgres
# ssh免密码登录密钥文件名SSH_KEY_FILE=id_rsa
SSH_OPTIONS="-o StrictHostKeyChecking=no -o UserKnownHostsFile=/dev/null -i ~/.ssh/${SSH_KEY_FILE}"echo failover.sh: start: failed_node_id=$FAILED_NODE_IDfailed_host=$FAILED_NODE_HOST \
old_primary_node_id=$OLD_PRIMARY_NODE_IDnew_main_node_id=$NEW_MAIN_NODE_IDnew_main_host=$NEW_MAIN_NODE_HOST## If there's no main node anymore, skip failover.if [ $NEW_MAIN_NODE_ID-lt0 ]; thenecho failover.sh: All nodes are down. Skipping failover.
exit0fi## 检查是否可以免密登录指定节点ssh-T${SSH_OPTIONS}${POSTGRESQL_STARTUP_USER}@${NEW_MAIN_NODE_HOST}ls /tmp > /dev/null
if [ $?-ne0 ]; thenecho failover.sh: passwordless SSH to ${POSTGRESQL_STARTUP_USER}@${NEW_MAIN_NODE_HOST} failed. Please setup passwordless SSH.
exit1fi## 如果down机的是从节点，跳过if [ $OLD_PRIMARY_NODE_ID !="-1"-a$FAILED_NODE_ID !=$OLD_PRIMARY_NODE_ID ]; then# If Standby node is down, drop replication slot.${PGHOME}/bin/psql -h${OLD_PRIMARY_NODE_HOST}-p${OLD_PRIMARY_NODE_PORT} postgres \
-c"SELECT pg_drop_replication_slot('${REPL_SLOT_NAME}');"  >/dev/null 2>&1
if [ $?-ne0 ]; thenecho ERROR: failover.sh: drop replication slot \"${REPL_SLOT_NAME}\" failed. You may need to drop replication slot manually.
fiecho failover.sh: end: standby node is down. Skipping failover.
exit0fi## 如果down机的是主节点，则提升指定从节点为主节点## 新的从节点由Pgpool投票选出echo failover.sh: primary node is down, promote new_main_node_id=$NEW_MAIN_NODE_ID on ${NEW_MAIN_NODE_HOST}.
## ssh到新的主节点并执行pg_ctl -D $PG_HOME promote提升从节点ssh-T${SSH_OPTIONS}${POSTGRESQL_STARTUP_USER}@${NEW_MAIN_NODE_HOST}${PGHOME}/bin/pg_ctl -D${NEW_MAIN_NODE_PGDATA}-w promote
## 提升失败退出，返回1if [ $?-ne0 ]; thenecho ERROR: failover.sh: promote failed
exit1fi## 提示提升成功并退出，返回0echo failover.sh: end: new_main_node_id=$NEW_MAIN_NODE_ID on ${NEW_MAIN_NODE_HOST} was successfully promoted to primary
exit0